Need recommendation for starter DMM

[gcc]

Hi,

Looking to get further into computer/pcb projects and I need a recommendation for a good DMM that will grow as I get further into robotics, arduino & other microcontrollers, flash, jtag, reverse-engineering, etc. I never really intend to do anything on the mains power side - this DMM will be strictly for working with microcontroller and PC-based (and HBA) based projects. Think Bunnie type projects, but less talented and in his early years.

1. Dave, in various blog posts, has recommended working with two DMMs. I'd like to start with one, but I acknowledge I'll need a second at some point.
2. As this is all lab work, I am okay with one of these in a bench DMM format, especially if I can get a greater feature set/accuracy from a bench unit at a lower price.
3. The Fluke 87 V seems to be an industry standard for professional level DMMs. And Dave also has a great offer in the EEVBlog Brymen BM235, which seems to be tweaked in the interest of greater safety measures. Since I won't be attaching to mains power, I am guessing that CAT IV protection is overkill for my projects.

Any recommendations or future proofing advice of these first home lab acquisitions would be hugely appreciated. Thanks!

[Skimask]

'cause the other 7,327 threads don't have enough information in them already...

[gcc]

Thanks for the quick reply, Skimask. I literally just found the forums, and I'm still parsing through the posts.  Got a link that would point me in the right direction?

[alsetalokin4017]

1. Sure, two or even more DMMs can be very useful. But you absolutely do need at least one, so it might as well be a really good one.

2. You can use a handheld DMM on the bench, but it's a lot harder to use a bench DMM in a portable situation -- and you _will_ be using your DMM off the bench. (Around the house, car, for friends, etc.) So make that "at least one" a handheld unit. Then when you need a second one, you can go one of two routes: get the El Cheepo from Harbour Freight (I have about six of these and they are just fine for most purposes) _or_ get that fine bench DMM with greater precision, 4-wire measurement capability, datalogging, etc. Or do both -- the El Cheepos are so cheap you can afford it, and you can treat it as a "throwaway" even though it works fine.

3. I like Fluke. I have an 83 that I bought new in (iirc) 1986 that has seen a _lot_ of rough field and lab use and still works perfectly, and I recently got an 87-III given to me by a friend, from someone's metrology lab surplus, still with a current calibration sticker on it, and I expect it to outlast me. I like Fluke.

I have a Simpson bench DMM but I hardly ever use it since the Fluke is right there handy, and when I need multiple DMMs I usually use both Flukes or the 87-III and one of the El Cheepos. Did I mention... I like Fluke.

[gcc]

My budget is ~$200 for a decent DMM. I think starting out, I will just be using it to diagnose/repair blown ICs and caps. I did a quick lookup of the non-DMM tools you mentioned and I think that's exactly what I am looking for. Huge thanks for giving me search terms to continue this research on. The red pitaya looks like a perfect platform to grown on.

Also, I understand that I'll eventually need hardware for jtag probing - any recommendations there, or are those unique to the manufacturer?

As for DMMs, I've was looking at used Fluke 87 V's on ebay, but I'm new to them and wouldn't know how to evaluate a used meter - either for authenticity or how out of calibration it is. I saw the teardowns from EEVBlog #99 ($100 Shootout) and the safety problems found in some brands. Until finding that shootout blog, my research was leading me towards something in the UNI-T brand. But the lack of proper fuses and all the board level mismatches from silkscreen design to actual layout was enough to remind me that inexpensive Chinese tools are usually not a good deal. Since the certifications are suspect from UNI-T, I worry that the accuracy at smaller levels would be suspect as well (pots!).

Also, when I say "never" mains, I'm a realist and know that someday I'll be looking at a dead outlet on a PDU in a rack, and be tempted to attach whatever DMM I have to troubleshoot. So "never" is really, maybe once every three years. I'm definitely not going to be tearing down large transformers, or DC motors, or three phase power.

For the types of projects that I want to do, PCB level signalling, I *think* I just need equipment tuned as small as I can reasonably afford. uA ranges, high read count rate (6000+), low-pass filter to drain tiny caps for replacement(?), fast continuity checking, good quality leads, etc.

I noticed that Fluke 189 have a data logger, so maybe that should rate higher on my feature set list.

Thanks for the response! This will give me plenty to research.

[gcc]

Thanks for the reply Alsetalokin -

I like Fluke as well. My dad has a Fluke 77 that he's had forever. They make them to last forever, which is why I am not afraid of paying a bit more for a DMM. I'm just trying to fine-tune it to the PCB level components that it will be used with 99.9% of the time. 0.01% of the time, I will be curious about a PDU outlet on a 230V circuit and the CAT ratings will save me from tomfoolery.

I was thinking about the Brymen EM285, EEVBlog edition for the secondary DMM. I'm just worried that as ICs continue to go lower in power, the EM285 isn't future proofed enough (0.4A/1000V). Perhaps I should go Fluke on the first and a decent bench DMM on the second, future purchase.

[daybyter]

Uni-t 139c ?

[helius]

I was thinking about the Brymen EM285, EEVBlog edition for the secondary DMM. I'm just worried that as ICs continue to go lower in power, the EM285 isn't future proofed enough (0.4A/1000V).

I don't understand this; are you talking about burden voltage? As long as the DMM has a microamps range, I don't see how low-power circuits would be a problem.
Also don't underestimate the importance of good probes. Most DMMs come with acceptable probes, but with much room for improvement.

[gcc]

I was considering a UNI-T DMM at first. I like the asthetics and overall industrial design. Researching reviews on them led me to EEVBlog, and Dave, albeit nit-picky at times, really hammered the UNI-T's. In #99, the UNI-T UT61D had some internal problems. The lead posts weren't a solid metal tube and would wear out over time, part of the EM foil shield was floated in the case, "built to cost" lower quality caps used, and trim pots. It's certainly a less expensive option, but there isn't any engineering above spec/price involved.

Dave may just personally hate the UNI-T's, but he goes further in a dedicated teardown of a UT71E in titled "Why UNI-T Meters Suck." I like the external aesthetics and it has multi-line readout, and watt functionality. But Dave hammered it on it's build to cost problems, odd trim pots, some packages were changed out from layout phase to flow, including the omission of HRC fuses for glass fuses. Externally, it was certed at CAT IV with those glass fuses, which is suspect.

[gcc]

Thanks for the reply helius -

I'm talking out of hat as I don't have much experience in correct amp ranges for current PC and HBA components, but I thought I should err on the side of smaller/lower is better and more future proof. Not sure if hard drives require more sensitive tools to diagnose a bad voice coil, etc. That may be a bad example, but it's the most sensitive PC thing I can think of atm.

[gcc]

It all boils down to cost. Fluke won't use trim pots because labor cost in US is more expensive, so using digital trimming makes more sense. In China, labor is cheap, so using manual trimming makes more sense in terms of cost. Unless the trim pot has really bad tempco or aging, I do not see why it will give inferior performance.

The teardown of the UT71E make it appear to be a troubled product, which may just be an outlier in UNI-T's QC process. The UT61E internals were certainly much cleaner, with no late phase refactors. As for the trim pots, I hadn't factored in the lower manual labor costs available in China. The main downside, for me, is that I intend use my DMM over a lifetime, as my dad has enjoyed with his Fluke 77. I'm not sure if that's a viable goal for our generation, but only time will tell. I would guess that digital trimming is more resistant to the natural wear and tear that lab tools endure over their use. At room temps, it may be a subtle delta.

[boffin]

Two answers;
Extech EX330.  It's a good all around (although the capacitance measurement is only for small values).  However the Frequency and mark/space (PWM power ratio %) is so freekin' handy when doing arduino control stuff.
EEVBlog BM235. Better overall meter, true RMS, but lacks the unbelievablely handy frequency & mark-space ratio that the EX330 does

Buy em both, because sometimes you need to measure two things at once.  $60 and $120, and still enough for a nice bottle of wine left over.

[gcc]

Buy em both, because sometimes you need to measure two things at once.  $60 and $120, and still enough for a nice bottle of wine left over.

Lol - the problem with wine and beer is that you only get to rent it. At this point, I'm leaning towards buying something a bit more expensive in the Fluke family and using it for 20 years, tomfoolery avoided. I'd rather overbuy on tools with a future, than have to forklift upgrade from a "just enough" purchase. Trying to find a good deal on a Fluke 1/287/9 or 87/9 with leads and case now.

[helius]

I would disagree that duty cycle is a commonly needed measurement. There are some times it is useful, but when you actually need to know the shape of a waveform DMMs are simply not the appropriate tool.

[gcc]

I would disagree that duty cycle is a commonly needed measurement. There are some times it is useful, but when you actually need to know the shape of a waveform DMMs are simply not the appropriate tool.

Helius - maybe wrong thread? or are you saying I should invest in a oscilloscope early?

[Lightages]

I need to say that I would not buy any Extech EX series meter. They are re-branded CEM meters and the quality control is not very good. There have been many reported problems here, and by Dave himself. I would rather recommend a Uni-T UT139C instead.

The BM235 that Dave is selling is a great meter. So is an Amprobe AM510 or higher model. Also consider the BM257S. For $200, even less, you can get the BM829S. Others to consider, Amprobe AM-140-A, Amprobe AM-270, Extech MM series, Fluke 17B+, Hioki, Yokogawa.

Anytime someone tells you to ignore safety, safety ratings of equipment, or don't worry, WORRY! The ratings are there for a reason. People have been injured and have died. "I don't know anyone who has had a problem" or "I have never had a problem" are personal opinions. I have never known anyone killed with a gun, therefore guns have never killed anyone?

The other thing to consider about cheap meters is that they might not give you a reliable reading. It is not just about safety to the user, but safety to the equipment or circuits you are testing. A wrong reading on a power supply could fry your circuit.

An old adage, "Buy quality, buy once. Buy cheap, buy many times".

[helius]

I was responding to post #16. The measurement of a PWM signal is called duty cycle, which is found on some DMMs, but most do not have it. In practice it is seldom needed because you can just measure its DC component.

[gcc]

I was responding to post #16. The measurement of a PWM signal is called duty cycle, which is found on some DMMs, but most do not have it. In practice it is seldom needed because you can just measure its DC component.

Ah, pulse width modulation.

However the Frequency and mark/space (PWM power ratio %) is so freekin' handy when doing arduino control stuff.

This is really helpful, since I plan on getting further into arduino, and I'm guessing this type of signalling is used in bus control protocols at a "layer one" level (if I can borrow OSI networking terms).

[tautech]

So you want to study up on DMM's ?
Study this:
https://www.eevblog.com/forum/testgear/hear-kitty-kitty-kitty-nope-not-that-kind-of-cat/

[gcc]

https://www.eevblog.com/forum/testgear/hear-kitty-kitty-kitty-nope-not-that-kind-of-cat/

Surprised the Fluke 87V failed at 1.5KV/2ohm. I'm new at this - is that under CAT III specs?


Interesting video showing some shortcomings of the Flukes under head to head testing. Again I'm new to this, but I wonder if this partially a count problem? The 87V having the highest count rate at 6K/20K for the Flukes, and the Brymen 869s at 50K (500K?).

I like the screen on the UNI-T UT181A, and a modified version passed these torture tests. If I were generalize across the DMM brands, I find the UNI-T's to be decent enough DMMs, but I think they have built to cost and when evaluated per component are not as good of a deal as the Brymen. Fluke is a clear industry leader, but comes at a price premium and may have rested on their laurels a bit as the early failure in the torture tests would indicate.

At this point, I'm favoring a less sexy Brymen 869s vs UNI-T181A TFT hotness. Or maybe these would pair well. A data logger UNI-T and the 500K count Brymen.

[gcc]

For the price of UT181A you can get a used 289.

In watching the workflow of the 289, the menu system gets in the way at times. The 181A uses a menu system as well, but had moved some functions out to one-touch buttons, which I like. Also, the 289's screen is one of the dimmer in Fluke's line. I imagine that both of these lines are due for a refresh to touch-screens, but I'm not sure when that refresh will hit the market. Also, I'm not sure how safe touch capacitance screens are. Perhaps touch screens won't make it to DMMs for safety reasons.

blueskull, as an owner of a Fluke 289, would you choose the 289 over a new 181A?

[tautech]

https://www.eevblog.com/forum/testgear/hear-kitty-kitty-kitty-nope-not-that-kind-of-cat/

Surprised the Fluke 87V failed at 1.5KV/2ohm. I'm new at this - is that under CAT III specs?

We all were. 
There's one hell of a lot of info in that thread, not just about DMM's but Joe's journey too, and the whys and why nots he's tested DMM's in the way he has.
Many get somewhat precious when their favourite DMM scores badly according to Joe, but don't skip through the thread too quick, you'll come out much wiser if you take the time to follow it through.
Me, the Fluke 15B is all I need for a portable DMM, they were intended for the Chinese market only and you used to be able to get them on eBay or Aliexpress but they've been superseded by the 15B+ and 17B+.
They're still quite adequate for basic EE needs and Dave's rebadged Brymen is a good bet too. Joe rated it highly.

[tautech]

@gcc
To confuse you more, there's this great thread too:
https://www.eevblog.com/forum/testgear/multimeter-spreadsheet/

[gcc]

@gcc
To confuse you more, there's this great thread too:
https://www.eevblog.com/forum/testgear/multimeter-spreadsheet/

Hahaha - thanks  !
I actually found this at the start of my search. It's been really handy to have a DMM list of mid-level to professional models, all in one place like this. It made it a little easier to spot ODMs in this market. Honestly, I'd love to get a Gossen, but at those prices, I think they are made out of rare German unicorn feathers. Those German unicorns are extra well engineered.

[Lightages]

I am a bit amused at the meters being considered given the title of the thread.